Those old structures also don't use steel reinforcement either. Our bridges and highway overpasses fail from the inside out due to rebar corrosion beneath the surface. They did a lot with what they had available to them regardless.
Look at the Atlantic Wall from WWII. It's falling apart from exactly what you stated. Water, freezing, and corrosion.
That is not a great example in this context IMO. The Atlantic Wall was never intended to last more than a decade I suspect. AH frowned on the use of concrete for his most important structures, he wanted those to last a thousand years, which concrete at that time would hardly last 100 years, but stone was up to the task, irrespective of rebar failing/corrosion/expansion. This nation has a number of TVA dams built prewar in a hurry that are way past their design life for concrete and must be dealt with soon. Personally, I am most impressed with the imported concrete used in the Florida Keys bridge system to Key West, that has withstood countless hurricanes, extreme temps, constant saltwater exposure and decades of traffic, and is still standing with zero Maintenace for over forty after being built over 110 years ago privately.
